The document FR-A-2 666 953 describes a terminal strip with insulation displacement contacts fitted in an insulating body and with push-in connecting pieces fitted to slide on the contacts. The insulating body has chimneys that open out in a "front" one of its faces, each chimney having one of the contacts extending therein. Each push-in connecting piece thus slides in one of the chimneys, along an insulation-piercing fork of the contact, between an inserted position connecting the insulated wire to the contact, and a withdrawn position for threading an insulated wire into the push-in connecting piece or disconnecting an insulated wire previously connected to the contact.
The push-in piece is either single, in which case it serves to connect one insulated wire to a contact, or else double, in which case it serves to connect two insulated wires simultaneously to two adjacent contacts of the terminal strip. The push-in piece, whether single or double, is made of plastic.
The single push-in piece has two facing longitudinal elongate members integral with an end actuating head and having mutually-aligned holes for threading the insulated wire through each of the elongate members. It also has a Vee to guide the insulated wire into the holes in the elongate members, this Vee being integral with the head and extending along the outside, in front of one of the members, with its bottom aligned with the holes and its opening facing towards the actuating head. The guiding Vee slides on the outside of one of the partitions of the chimney when the members slide on either side of the contact along the insulation-piercing fork of the contact.
To improve the mechanical strength of the insulated wire connected to the contact, a calibrated gripping slit is provided in the chimney wall along which the guiding Vee slides, to grip the insulated wire. It is therefore necessary to impart to the single push-in connecting piece a total force comprising the force required for inserting the insulated wire into and along the length of the insulation-piercing fork of the contact, plus the force required to insert the insulated wire into and along the calibrated gripping slit.
The double push-in piece has two pairs of elongate members arranged side by side and two guiding Vees both on the same side of the members, all of which are fast with the end actuating head. The total force needed to operate the double push-in piece is twice that needed for the single push-in piece. It may be at the limit of finger force when actuating the double push-in piece from its withdrawn position to its inserted position.